Photosensitive Epilepsy

How does it affect people?

Only about 3-5% of people with epilepsy are photosensitive. This reaction is diagnosed by EEG precautionary measures are advised to affected persons. Anyone can have a seizure if they watch light flickering at a fast enough frequency. A slower frequency (most commonly 15 - 20 flashes per second or hertz) is sufficient to trigger a seizure in someone who is photosensitive. However a hertz rate as low as 5 or up to 30 may still provoke some persons. In some cases it is the intensity of the light rather than the flicker which provokes the seizure. In almost all cases the person experiences a generalised tonic-clonic seizure there and then, in which they lose consciousness, fall on the ground, and convulse for approximately 1 - 3 minutes.